CASCA 2010: planets session

NIR from hot Jupiters (Bryce Croll):

Hot Jupiters are tidally locked, and one expects their properties to depend on the amount of heating. He tested this with four known hot Jupiters. To get good photometry, he used WIRCAM out-of-focus (!). This lets them detect the thermal emission from hot Jupiters (millimagnitudes). "Hot" and "hotter" distribute heat very effectively, though "hotter" shows abnormally low H-band emission; maybe an absorber? "Even hotter", on the other hand, doesn't distribute heat very effectively. "Hottest" shows redistribution within the hot side but not between sides, plus evidence for a thermal emission deep in the atmosphere.  Many more CFHT observations are planned.

Music of the Spheres: Results from the Kepler Mission (Jason Rowe):

Kepler's a 1m space telescope designed for steady monitoring of a fixed field of 100000 stars, looking for exoplanets and asteroseismology. CCDs were placed so that the brightest stars fall into the gaps. Kepler's bandpass is more or less white light (400-900 nm). Measurements as good as one part per million for  many stars; Kepler's working very well. The parameters you fit directly include stellar density. The smallest planet so far is ~Neptune-sized, but some secondary transit measurements show you could detect a terrestrial transit. In asteroseismology they should get p-modes for every star brighter than ~12 mag. Also some weirdos like helium white dwarf companions, for which radial velocity followup has begun. Apparently Kepler also has Guest Observers and Target of Opportunity arrangements.   Quite what this means I'm not sure, since the instrument isn't pointed.

In questions, they do have lots of earthlike transit candidates - but they get lots of false positives from photometry alone, let alone grazing transits by bigger objects.

SPI or Spin-up? An UV Investigation of Activity on Exoplanet Host Stars (Evgenya L Shkolnik)

"SPI" is "star-planet interaction", meaning magnetic. Spin-up is tidal effects of the planet on their stars. These should occur since the planets are so close to their stars. Both should show up as increased stellar activity (hence the UV). Looking at X-ray data, there's debate about whether this is observed. She used GALEX (175-275 nm). GALEX sees almost every exoplanet host star (that's in its field of view). Given 135 GALEX detections, start with close-in planets seem to be ~2x brighter. (Planet distance is a bimodal distribution, so there's a natural dividing line here; we think it's migrated versus not migrated.) A few transiting systems have been observed to have abnormally rapidly rotating stars; if this is a general phenomenon, gyrochronology goes out the window. The exceptions, stars that aren't active in spite of close-in planets may be explicable in terms of some scattering models but not others, and in fact the exceptions are more eccentric, consistent with the potentially recent scattering models.

Super-Earth Transit Search with the MOST Space Telescope (Diana Dragomir)

Start with radial velocity candidates from HARPS; F, G, K with 2-20 Mearth planets. MOST watches during the transit window. Key transit parameters are period, phase, duration, and depth. Diana's idea is to use Bayesian methods to fit the model, which is feasible mostly because the HARPS candidates provide a drastically reduced parameter space. (Ew! She uses JDs!) This parameter space needs to be very finely sampled to avoid underestimating the depth. (She's using grid sampling rather than MCMC because of the small low-dimensional parameter space.)

Ultra-Wide Trans-Neptunian Binaries (Alex H. Parker)

You classify TNOs based on their resonance with Neptune: the plutinos, for example are roughly 3:2 times the period. The big question is how the TNOs got there, since they haven't had time to form in situ. One answer is that as the giant planets moved out to their current positions they scattered the planetoids out into the outer solar system. This talk is about binaries; binaries are present throughout the solar system. Binary asteroids are different, as they tend to have large mass ratios and tight circular orbits, suggesting a collisional origin. The TNOs have lots of binaries, with a wide range of eccentricities and often modest mass ratios. These binaries are interesting observationally because you get mass measurements. Wide binaries are resolved with Gemini, and they're so delicate you can test dynamical ideas with them. Their formation mechanism is debated, maybe three-body exchanges, maybe temporary capture into chaotic orbits, but the mutual orbit distribution should allow them to be distinguished. His sample is >0.5'' apart and mags differing by <1.5. Typicallt separations ~1'' and mags ~24. Terrestrial parallax allows measurement of things like the direction of the orbital axis. The observed distribution doesn't really fit with either formation model. You can also use these to look at the number of ~1km objects in the Kuiper belt, since these objects will eventually break up such a system. These small objects  can't be made through accretion or collision, they have to be primordial.

HST Compositional Survey of Faint Kuiper Belt Objects (Wesley C. Fraser)

The idea is to look at chemical gradients in the protoplanetary disk; this is closely related to understanding their scattering history, which is what dominates their current dynamics. Compositionally, only the biggest can retain methane (as it evaporates on a timescale of thousands of years). The fainter ones you don't get much in the way of lines, so the data is mostly colour (some are neutral, some are quite red). In the IR you do see deep water ice on certain objects ("family members" in resonances?) but not on others. It's a little puzzling what these objects are actually made of. Fortunately WFPC-3 is almost ideal for this work, with filters for water ice, methane, and a couple of useful narrow-line filters. The colors show evidence of a mix of water ice and some red gunk in varying proportions. Centaurs, objects that have been scattered further into the solar system show evidence for solar processing. Other objects are more mysterious.

Searching for Main-Belt Comets Using the CFHT: Final Results (Alyssa Gilbert)

Main-belt comets reside in the asteroid belt but show cometary activity. Their origin is unknown; formed in situ, which would be weird, since we don't expect ice within the orbit of Jupiter, or maybe formed further out and somehow got stuck in the asteroid belt. Only five objects are known, and have been recently found. Small bodies are interesting because they form in different parts of the solar system, and they don't have sesimology or weather, so they provide fairly direct pictures of the structure of the early solar system. To find these objects, she used the CFHT legacy survey data. The cadence is 3 observations in one night followed by another a night later (weather permitting). Automated object selection not terribly effective; visual inspection of 25000 objects worked better and found one. (Somebody has a very high tolerance for boredom...) Unfortunately the object wasn't noticed until a year after the observations, so even though a rough orbit was found the object was lost.  Asteroids activated by collision might produce an appropriate number, but the activity of some of these objects seems to be periodic, which is weird. Capture from the outer solar system should provide too many.

No comments: